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From: Don Yuniskis <dgy@rtd.com>
Message-Id: <199704021543.IAA08149@seagull.rtd.com>
Subject: Re: wd and funky geometry (understood?)
To: terry@lambert.org (Terry Lambert)
Date: Wed, 2 Apr 1997 08:43:05 -0700 (MST)
Cc: bde@zeta.org.au, freebsd-hackers@freefall.FreeBSD.org (FreeBSD hackers)
In-Reply-To: <199703171843.LAA08211@phaeton.artisoft.com> from "Terry Lambert" at Mar 17, 97 11:43:45 am
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It seems that Terry Lambert said:
> 
> > >However, *both* drives have a BIOS geometry of 611/16/63.  (Sorry,
> > >my ancient BIOS does not support "user configurable" geometries
> > >so this was the closest geometry I could find -- hence the reason
> > 
> > What's the problem?  The BIOS uses the fudged geometry that you told it,
> > but the FreeBSD driver knows better - there is no reason for it to use
> > a fudged geometry.
> 
> The disk is shared with DOS and uses the DOS MBR.  THe DOS MBR will
> use the fudged geometry, and the BSD DOS partition table entry must
> be in the fudged geometry to make the DOS MBR happy to boot it.

*Yes*!  (whew, I *thought* that's what I was saying  :-(

> > Of course you must use a consistently fudged geometry for everything
> > related to the BIOS.
> 
> Like multiplying the C/H/S value by the fudged geometry in protected
> mode to find the BSD boot and disktab data.

And doesn't FBSD need to know the DOS geometry (or "virtually"
reINIT the drive) to be able to find all of the DOS sectors
when it mounts the msdosfs?
--don